The present invention relates to a process for rapidly drying and hardening a film-forming material.
Heretofore, in the drying and hardening of a film-forming material from which a film can be formed by oxidation drying, a catalyst which comprises a major proportion of a lead soap and a minor proportion of one or more metallic soaps selected from the group consisting of cobalt, manganese, zinc, calcuim and zirconium soaps has been used. Among these dryers, the lead soap is particularly excellent in both internal drying property and surfaces drying property. However, this material is designated as a harmful metal and its discharge is severely limited. Also, lead and its compounds are regulated in their use as an additive for paints and varnishes.
Therefore, there has been a need for development of a lead-free dryer possessing the same effect as the lead dryer or a system including the same. For example, U.S. Pat. No. 2,739,905 has proposed the use of a zirconyl soap and U.S. Pat. No. 2,739,902 has proposed the use of a zirconyl soap in conjunction with a cobalt soap or a manganese soap. Also, the use of phenanthrolines in conjunction with a manganese soap has been proposed in U.S. Pat. Nos. 2,526,718 and 2,565,897. In addition, a dryer comprising zirconium and cobalt combined with each other through oxygen is disclosed in "Paint Technology", 35, (8), pages 18 to 19. Further, in Japan, a zirconium dryer is disclosed in "Toso Gijutsu (Painting Technique)", Dec., 1972, pages 86 to 87. These dryers all use a zirconium soap and are reported to have a catalytic performance superior to that of the prior cobalt soap alone. However, when these dryers are carefully examined, it is found that the surface drying and internal drying properties are not as good as lead containing dryers.
In earlier years, one of the applicants found that one type of a stabilized coordination compound formed by the coordination of a metallic soap such as a cobalt or manganese soap with a titanic acid ester such as titanium tetraisopropoxide and titanium tetra-n-butoxide exhibited excellent performance as a dryer for an oxidation polymerization driable film-forming material and obtained a patent therefor (reference is made to Japanese Pat. No. 604964). However, the titanic acid ester usually is highly reactive and reacts with water or functional groups contained in the film forming material, such as a hydroxyl group, carboxyl group, epoxy group, acetate group and the like to cause gelation in a short period of time, whereby it often becomes practicably useless and loses its economic value.
As a result of our study directed toward development of an excellent drying hardener for a film which is free from lead, we have found that a complex formed from an alkoxy radical containing zirconium compound and a cobalt carboxylate is very useful as a drying promotor for an oxidation polymerization driable film-forming material. This finding is a basis of this invention.